The term “dag” is to be interpreted in this specification to mean hair and other material, such as mud and dung, which has become hardened or clotted to form ball-like masses which are attached to the carcass of an animal.
Where reference is made in this specification to a single integral element, this is to be interpreted as including an element made up of separate parts which are joined together in a permanent manner such as by welding or permanent bonding. Where reference is made to a cylinder, this is to be understood as a cylinder of circular cross-section. The term “cylindrical” is to be understood in a corresponding sense.
The invention has been developed primarily for removing dags from carcasses in abattoirs and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to that particular field of use.
A known dedagging implement includes a rotor having lobes for wearing, and cutting, away dag from a carcass. Certain dag, known as winter dag, has a brittle, hard outer surface which can contain dry, dust-like material. As the rotor removes the dag, the outer surface is generally broken and the dust-like contents contaminate the implement and foul the rotor. Some of the dag remains attached to the lobes and only becomes dislodged when the lobes undergo a further revolution and contact the carcass again. Thus, the dag is redeposited on the carcass. Any liquid with which the dag material mixes causes the material to form a mud smear on the carcass.
Sticking of the dag to the rotor is particularly prevalent in the case of dag known as summer dag. Summer dag is softer than winter dag, and is of a sticky, toffee-like consistency. As the rotor turns, the dag, which has been at least partially broken up, becomes smeared on the carcass by the lobe. Some of the dag does, however, become dislodged from the rotor as it rotates, and is flung onto the inner walls of the implement, to which it sticks, thereby fouling the equipment.
Consequently, the dedagging process using such implements is not as efficient or effective as it should be. This causes difficulties in satisfying existing food hygiene requirements.
Another disadvantage of existing dedagging implements is that the broken-up dags enter, and contaminate, bearings which support the implements' rotors. This necessitates time consuming, expensive and complicated maintenance procedures.
Existing implements also suffer disadvantages relating to safety of use. The lobes of the rotors project though openings in the implements' housings. Should an implement be activated while facing towards an operator, parts of the operator's body can inadvertently come into contact with the lobes. This can prove dangerous or even fatal.
A further disadvantage of known dedagging implements relates to their having rotors which include shafts and separate lobe elements. The shafts have central portions of hexagonal cross-section. Each element includes a central ring having an aperture shaped complimentarily with respect to the shaft, and the elements are slidingly received on the shafts. Integral lobe fingers project radially outwardly from the rings. Dag material penetrates between adjacent elements forcing them apart. Some of the material is deposited on the axially outer sides of the outermost elements. As the elements are forced apart, this outer material is caused to enter, and contaminate, the bearings. Furthermore, the lodging of contaminants between the elements affects the balance of the rotors, and this contributes to wear of the bearings. Once again, time consuming, expensive and complicated maintenance is required.
Another disadvantage of known dedagging implements relates to the design of their rotors. The rotors of certain known implements have lobes which, although effective at removing dag material from a carcass, are shaped so as not to fling the dag away from the lobes effectively. Thus, the dag tends to stick to, and accumulate on, the rotor. In the case of other known implements, the rotor has lobes positioned successively along the axis of the rotor, adjacent lobes being circumferentially spaced from each other and shaped such that dag material tends to be deflected so as to bypass the lobes as they rotate, rather than being “caught” by the lobes.
A further disadvantage of known dedagging implements relates to their having rotors which are actuated by compressed air. This method of actuation produces insufficient power and results in unacceptable equipment noise levels.
Known dedagging implements use vacuum systems to evacuate contaminants that have been removed from carcases. A known vacuum system includes a vacuum tank and a relatively low powered vacuum pump. The pump is used to produce a vacuum pressure in the tank while a valve between the tank and the implement is closed. When the valve is opened, the initial vacuum pressure in the tank is sufficient to cause a strong suction effect to remove dag material from the implement. However, as the pressure in the tank reduces and reaches equilibrium with the suction pressure of the vacuum pump itself, the effectiveness of the suction decreases and becomes inadequate.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art or to provide an alternative.